In the end, you are just renting well maintained server farms (well, a specific percentage of operational time of some of the servers in them). There is absolutely no appeal for large technology-based companies do this once they can (the following is the lowest scale example) afford to maintain their own servers, while potentially renting a few offsite backups in other areas of the world (again, this is just the lowest-scale architecture starting at which Serverless is always the worse option).
Existing solutions are extremely over-engineered. It can be excused with "officially planning for the use-case where maximum scalability is required", but it's almost certainly a pretense to sell "certifications", aka "explaining our own convoluted badly documented mess". What this actually means is that many SWE's who are good enough to learn to use Serverless effectively, can learn any other framework that allows building distributed systems across server nodes with equal effort. Why would I base my whole business on your vendor locked, sub-optimized dumpster when I can do the same on an infinitely scalable VM networks, that can be ported to literally any vendor who supports $5/mo VMs (or, you know, self hosted if my company is large enough)?